Objective: To compare the use of dietary supplements and nonprescription medications as reported on a written medical questionnaire with use reported during a structured interview. Design: We conducted a prospective study of 200 subjects randomly selected among patients undergoing a periodic health examination in two divisions of the Department of Internal Medicine at Mayo Clinic Rochester - 100 patients from a national cohort of executives and 100 community patients. Material and Methods: Written information on self- reported use of supplements and nonprescription medications was obtained as part of a comprehensive medical questionnaire. Subjects were then interviewed and asked about the use of supplements and nonprescription medications. In addition, the reason for using supplements was elicited and recorded. Results: The prevalence of use of dietary supplements was 30.5% by written self-report in comparison with 61.0% reported during the structured interview. The results were consistent between executive and community patients. In response to questions about taking nonprescription medications, 24.5% of patients reported such use on the medical questionnaire in comparison with 42.5% when interviewed. The most common dietary supplements taken were multivitamins (41.5%), followed by vitamin E (24.0%) and vitamin C (23.0%). The most common nonprescription medications taken were aspirin (16.5%) and ibuprofen (13.0%). Most frequently, patients indicated that they were using supplements to promote health. Conclusion: In this study, half the patients who took dietary supplements and almost half who took nonprescription medications did not report them to their healthcare provider on a written questionnaire, even though this information was requested. Patients should be specifically asked about use of dietary supplements and nonprescription medications, even if written information about such use is provided.
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